The first map is called a "A land of Forest". It's a big map: 256x256. Playing CPU Ultras is fun on this map because you have a lot of time before they build up an army and and attack you. There's a gold and stone "oasis" in the center of the map that tend to be a popular place for battles.
The second map is called "Forest Frenzy". It's a great place for testing out your faction because it's a standard map on 64x64 size.
The third map is called "Communal Gold", and it's exactly that. This map is a map for dominating the CPU, even an Ultra. The key is to win over the center of the map, where the gold is. This map is good for testing out units you've made to see if you like them, and also for testing particle prog's.